Method of stripping



Patented-May 15, 1934 UNITED STATES PATENT OFFICE METHOD OF STRIPPING NoDrawing.

Application November 21, 1930,

Serial No. 497,336

6 Claims.

This invention relates to a method of stripping the color of dyedtextile material, and relates more particularly to the stripping oftextile materials made of cellulose acetate or other organic derivativesof cellulose.

- An object of my invention is to strip the color of dyed textilematerials in an expeditious manner. A further object of my invention isto remove the color in whole or in part of dyed textile 10 materialscontaining organic derivatives of cellulose. Other objects of thisinvention will appear from the following detailed description.

It is often desirable to strip or remove the color or dyed fabrics inorder to render them capable of being dyed in a different color orshade. Thus if errors have been made in the dyeing of fabrics, hosieryand the like so that an undesired color is imparted thereto or thedyeing is streaky, the usual practice is to remove the color and thendye the materials to the desired shade. However the stripping of textilematerials containing cellulose acetate or other organic derivatives ofcellulose which have been dyed with dispersed dyestufls has heretoforenot been commercially successful when the ordinary methods of strippingare employed.

I have found that textile materials containing cellulose acetate whichhave been dyed with dispersed dyestuffs may be stripped to the extentrequired in commercial operation if the same are first treated with areducing agent, preferably in the presence of an acid, and then treatedwith an oxidizing agent, also preferably in the presence of an acid.

In accordance with my invention, I strip a dyed textile material byfirst treating the same with a reducing agent and then treating it withan oxidizing agent.

The textile materials to be stripped in accordance with this inventionmay be yarns, woven or knitted fabrics, or articles of apparel such ashose, dresses, underwear and the like. While this invention may be usedfor the stripping of textile materials containing any kind of fibre, itis of particular importance in the stripping of textile materialscontaining filaments of organic derivatives of cellulose such as organicesters of cellulose and cellulose ethers. Examples of such organicesters of cellulose are cellulose acetate,

cellulose formate, cellulose propionate and cellulose butyrate, whileexamples of cellulose ethers are ethyl cellulose, methyl cellulose andbenzyl cellulose. The textile material may be a mixed materialcontaining yarns or filaments of the organic derivative of cellulose andother textile fibres such as cotton, wool, silk or reconstitutedcellulose.

The textile material to be stripped may have been previously dyed withany dyestulf, but this invention is of particular importance inconnection with the stripping of organic derivative of cellulosematerial which has been dyed with dispersed dyes, that is waterinsoluble dyes that are applied in finely dispersed or colloidalsuspensions, since these dyestuffs are quite fast. Examples 05 of suchdispersed dyes are amino-azo-benzene derivatives, benzene-azo-naphthylamine derivatives, naphthalene-azo-aniline derivatives oramino-azo-naphthalene derivatives, as more particularly described in theU. S. patent to Ellis 1,618,- 413 of February 22, 1927; nitroderivatives of diaryl amines as described in the U. S. patent to Ellis1,618,415 of February 22, 1927; vat dyestufl's of the anthraquinoneseries in unreduced state as described in the patent to Ellis 1,641,965of 7 Sept. 13, 1927; unsulfonated stilbene compounds as described inpatent to Ellis 1,694,414 of December 11, 1928, etc.

To effect the stripping, the textile material is first treated with areducing agent which may be an aqueous solution of zincsulfoxylate-formaldehyde or sodium sulfoxylate-formaldehyde, preferablyin the presence of an acid and at elevated temperatures of say 160 to190 F.

After treatment with the reducing agent, with 86 or without previouswashing, the material is then treated with an oxidizing agent such as anaqueous solution of sodium hypochlorite, potassium hypochlorite orcalcium hypochlorite, pref erably in the presence of an acid andpreferably 9 at ordinary temperatures.

The stripping process may be conducted so that all of the color isstripped from the textile materials or only partially stripped so thatthe shade remaining does not interfere with the color to be imparted tothe textile material by subsequent dyeing.

In order further to illustrate my invention, but without being limitedthereto, the following specific example is given.

Example 100 parts by weight of hosiery made of cellulose acetate yarnwhich have been dyed with a dispersed dyestufl is entered in a machinecontainallowed to run for 30 minutes at 180 F. The

machine is then drained and refilled with water to rinse the goodsthoroughly so as to remove all traces of the zincsulfoxylate-formaldehyde and the machine is then drained. There is thenadded to the machine a solution of the hypochlorite of sodium or calciumof 1 Tw. and 5 parts by weight of acetic acid (56% strength) and thegoods are allowed to remain in this bath at room temperatures for 30minutes.

The machine is then drained and refilled with water and the goods wellrinsed. Thereupon the machine is drained and refilled with water and onepart by weight of sodium bi-sulfite, as antichlor, is added to the bathand the goods treated for 10 minutes at ordinary temperature. Themachine is then drained and refilled with plain water and the goodsrinsed.

It is to be understood that the foregoing description is given merely byway of illustration and thatanany variations may be made therein,without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patentis: I

1. Method of removing color from a dyed textile material containingyarns of organic derivatives of cellulose comprising treating thetextile material with a reducing agent comprising a sulfoxylate and thentreating the material with an oxidizing agent comprising a hypochlorite.

2. Method of removing color from a dyed textile material containingcellulose acetate comprising treating the textile material with areducing agent comprising a sulfoxylate and then treating the materialwith an oxidizing agent comprising a hypochlorite.

3. Method of removing color from a textile material comprising yarns ofcellulose acetate which have been dyed with a dispersed dyestuflfcomprising treating the textile material with a reducing agentcomprising a sulfoxylate in the presence of an acid and then treatingwith an oxidizing agent comprising a hypochlorite in the presence of anacid.

4. Method of removing color from a textile material comprising yarns ofcellulose acetate which have been dyed with a dispersed dyestuflcomprising treating the textile material with zincsulfoxylate-formaldehyde in the presence of an acid and then treatingwith an oxidizing agent comprising a hypochlorite in the presence of anacid.

5. Method of removing color from a textile material comprising yarns ofcellulose acetate which have been dyed with a dispersed dyestuffcomprising treating the textile material with zincsulfoxylate-formaldehyde in the presence of an acid and then treatingwith a hypochlorite in the presence of an acid.

6. Method of removing color from a textile material comprising yarns ofcellulose acetate which have been dyed with a dispersed dyestuffcomprising treating the textile material with zincsulfoxylate-formaldehyde in the presence of an acid at a temperature of160 to 190 F., rinsing the material, treating with a solution of ahypochlorite in the presence of acid at room temperatures, washing thematerial, and then treating with an anti-chlor.

KENNETH CLARKE LOUGHLIN.

